Positive feedback of interparticle interaction on magnetic hyperthermia

The work deals with experimental and theoretical study of magnetic hyperthermia produced by a system of immobilized magnetically interacting multidomain ferromagnetic particles, placed in an oscillating magnetic field. The intensity of heat production was measured by direct calorimetry of heat evolution from model epoxy composites with the particles. Magnetite particles with weight averaged diameters 65 and 190 nm, and metal iron particles with weight averaged diameter 85 nm were used as fillers, which volume fraction in composites was up to 36%. Sine-wave magnetic field with the strength 1.75 kA/m at the frequencies 100, 150, 213 kHz was elaborated in hyperthermia heating. Theoretical consideration was focused on the influence of dipole-dipole interaction on the relaxation time of the particle magnetization in the oscillating field. The results show that the interparticle interaction significantly enhances the intensity of the heat production This effect must be considered at the practical organization of this method for therapy of cancer diseases.